Dual fuel system

ABSTRACT

A dual fuel system for an internal combustion engine having a carburetor supplied with high volatility fuel for engine starting and then with regular fuel for continued normal engine operation, an on board still being used to distill the high volatility fuel from the regular fuel during engine operation, the thus distilled fuel being stored for use during the next engine start-up.

United States Patent 1 1 1 1 3,788,283

Perry I 1 Jan. 29, 1974 [5 1 DUAL FUEL SYSTEM 2,884,917 5/1959 Quinby123/133 3,498,279 3/1970 Seeley, Jr 123/122 F [75] Invent James Perry3,688,755 9/1972 Grayson et a1 123/3 [73] Assignee: General MotorsCorporation,

Detroit, Mich. Primary ExaminerAl Lawrence Smith Assistant ExaminerW. H.Rutledge, Jr.

[22] Fled: 1972 Attorney, Agent, or FirmJ. L. Carpenter et a1.

[21] Appl. No.1 301,653

[57] ABSTRACT [52] US. Cl 123/3, 123/133, 123/179 G,

123/180 R, 123/127 A dual fuel system for an internal combustion engine5 Int CL oz 51/00, F02m 3 3 oo F02n 17/04 having a carburetor suppliedwith high yolatility fuel 123l122 E, 34 R 34 A 35, 127 tinued normalengine operation, an orTbozHl still being used to distill the highvolatility fuel from the regular fuel during engine operation, the thusdistilled [56] References Cited f l b t d f d th UNITED STATES PATENTSurge emg s ore or use urmg e next engme start- 2,625,920 1/1953 Farrell123/133 3 Claims, 4 Drawing Figures PATENTED JAN 2 9!?174 SHEET 1 OF 2PAIENTED 3.788.283

sum 2 or 2 FROM FUEL TANK DUAL FUEL SYSTEM This invention relates to afuel system for internal combustion engines and, in particular, to adual fuel system for selectively supplying a high volatility fuel and aregular fuel to an engine with on board partial distillation of theregular fuel to provide a high volatility or low emissions startingfuel.

It is well known that the use of a high volatility fuel in an internalcombustion engine during engine start-up will permit faster enginestarting due to more rapid vaporization of such high volatility fuel inthe induction system of the engine and the use of such a fuel willreduce cold start exhaust emissions as compared to the use of a regularfuel such as gasoline in the engine during cold starts. However, thecontinued use of such a high volatility fuel in the engine after enginewarm-up is normally not practical due to economic considerations, theuse of regular gasoline in a conventional fuel system being preferredfor continued engine operation. Because of this, various dual fuelsystems have been proposed in the past wherein high volatility fuels areused for engine start-up and a conventional fuel used for continuedengine operation, but such systems have been somewhat complex and verycostly.

It is therefore the primary object of this invention to improve a fuelsystem for an internal combustion engine in which two fuels areselectively supplied to the engine as required with both fuels beingobtained from a single fuel inlet.

Another object of this invention is to improve a dual fuel system for aninternal combustion engine wherein partial distillation of aconventional gasoline occurs during engine operation to provide a highvolatility, low emission starting fuel for the engine.

These and other objects of the invention are attained by a dual fuelsystem for the internal combustion engine of a vehicle wherein adistillation unit is used to partially distill regular gasoline usingheat from the engine, the thus distilled high volatility fuel beingstored and then selectively pumped to the float bowl of the enginecarburetor for use during engine start-up after which regular gasolinefrom the fuel reservoir for the engine is used to effect continuedoperation of the engine.

For a better understanding of the invention, as well as other objectsand further features thereof, reference is had to the following detaileddescription of the invention to be read in connection with theaccompanying drawings, wherein:

FIG. 1 illustrates schematically the internal combustion engine of avehicle, fuel being supplied to the engine by a dual fuel system inaccordance with the invention;

FIG. 2 is a sectional view of the distillation apparatus ofthe dual fuelsystem of FIG. 1 with the fuel flow control system to it shownschematically.

FIG. 3 is a schematic illustration of the carburetor float bowl fuelsupply and drainage system of FIG. 1; and,

FIG. 4 is a schematic diagram of the electrical control circuit of thedual fuel system of FIG. 1.

Referring now to FIG. 1, reference character designates an internalcombustion engine of a vehicle having an air cleaner 11 and carburetor12 mounted thereon for supplying an air-fuel mixture to the inductionpassages of the engine. As shown, the engine is provided with a coolingsystem including a radiator 14 connected by an intake hose 15 to receiveengineheated coolant fluid, such as water, which is cooled during itspassage through the radiator and then is discharged back through aconduit 16 to the engine 10, in a conventional manner.

Now, in accordance with the invention, dual fuels are supplied to theengine 10 from a single source of fuel, such as from regular fuelcontained in a fuel tank or reservoir 20. Regular fuel, such asgasoline, is supplied to the engine from the fuel reservoir 20 via aconduit 21, a fuel pump FP-l and a conduit 22 through a shuttle valve 23and conduit 24 to the float bowl 21a of the carburetor 12. Regular fuelis also supplied through the fuel pump FP-l and through a conduit 25 ascontrolled by a solenoid valve SOL-V therein to the inlet of adistillation unit 40, wherein partial distillation of the fuel producesa high volatility fuel, with the fuel remaining after the distillationof the high volatility components therefrom being returned via a conduit26, fuel pump FP-3 and conduit 27 back to the fuel reservoir 20. Theheat necessary to effect distillation of the fuel within thedistillation unit 40 is obtained from the heated fluid discharged intoradiator 14, this fluid passing via conduit 31 to the distillation unitand is returned from the distillation unit back to the radiator viaconduit 32.

High volatility fuel produced in the distillation unit 40 is stored inthe bottom thereof and delivered to the float bowl of the carburetor foruse during engine startup through a conduit 33, fuel pump FP-2 andconduit 34 as controlled by the shuttle valve 23 which controls the flowof selected fuel through the conduit 24 into the float bowl 12a of thecarburetor. As will be described in greater detail hereinafter, topermit the use of only high volatility fuel during engine start-up,regular fuel is drained from the float bowl of the carburetor, afterengine shutdown, through a conduit 36 connected to the previouslydescribed return fuel conduit 26.

Distillation unit 40, which is mounted in air flow relationship to theradiator for cooling by air drawn thereover by engine fan 17 includes anouter finned condenser tube housing 41 closed at its bottom end by anapertured base plug 42 and apertured cap 43, the latter being secured tothe tube housing as by a welding. In the upper end of the tube housing,there is positioned a fuel evaporation unit in the form of a boilerbody, generally designated 44, having a stepped plug portion 45 closingoff the upper end of the tube housing and, having its depending boilerportion 46 extending partway through the tube housing, the boilerportion 46 being provided with a helical groove 47 gasoline flow path onthe exterior thereof. The boiler body is provided with an axialextending, internal, stepped bore 48 in which a fluid inlet tube 50 issecured as at the reduced end of the stepped bore 48 to define with thestepped bore a hot fluid inlet passage 51 down through the boiler withinthe inlet tube and a return passage 52 defined by the outer periphery ofthe inlet tube 50 and the enlarged bore wall of the stepped bore 48. Hotfluid is admitted into the inlet passage from conduit 31 via a radialpassage 53 in the plug portion 45 of the boiler body 44 in communicationwith the upper end of the inlet tube 50 and this fluid is thendischarged to the conduit 32 via a radial passage 54 within this plugportion in communication with the enlarged portion of the stepped bore48 whereby hot fluid, as from the radiator, at for example a temperatureof F. is introduced into the boiler body for circulation therein so asto vaporize the high volatility components of the gasoline flowing downthe helical groove 47 gasoline flow path on the exterior of this boilerbody.

Liquid gasoline delivered to the distillation unit 40 via the conduit 25as controlled by the solenoid valve SOL-V flows through a radial passage55 in the plug portion 45 of the boiler body 44 to which conduit 25 issuitably secured and then down through an axial extending passage 56with flow therethrough controlled by a metering orifice 57 of apredetermined size and then through a splash tube 58 positioned in thepassage downstream of the metering orifice, the lower end of the splashtube 58 being positioned closely adjacent to the upper portion of thehelical groove 47 gasoline flow path whereby liquid gasoline dischargedtherefrom will flow down the helical groove flow path in heat exchangerelationship to the coolant liquid being circulated within the boilerbody.

Since this circulating coolant fluid is introduced at a temperature of,for example, 180 F. and since the liquid gasoline consists of variousmixtures of gasoline components which boil within an approximate rangeof 95 F. for pentane to about 450 F. for hendecane, the highervolatility components of the gasoline will vaporize as the gasolineflows down over the flow path on the exterior of the boiler body, whilethe non-vaporized or undistilled fuel will be discharged from the flowpath into a drip pan 60 positioned within the tube housing 41 below theboiler body 44, this drip pan being provided with a discharge duct 60aconnected to conduit 26 whereby this fuel is returned to the fuelreservoir by the fuel pump FP-3.

The higher volatility fuel thus vaporized, as described above, will thencontact the interior wall surface of the finned condenser tube housing41 to be cooled thereby to condense as a liquid distillate on thissurface and flow down to the lower or reservoir portion 61 of thecondenser tube housing defined as the chamber therein between the baseplug 42 and the drip pan 60.

Detection of the amount of distillate, in the form of high volatilityfuel, in the reservoir portion 61 of the distillation unit 40 isaccomplished by a conventional fuel tank fuel gauge. For this purpose, afloat guide tube 62 is secured to extend upward through the apertures inthe base plug 42 and cap 43 and it is provided with a fluid dischargeport 62a in the wall thereof positioned closely adjacent to the baseplug 42 and has its lower end, which extends outward from cap 43,connected to the conduit 33.

The guide tube 62 has a calibrated resistance wire 63 mounted along theexterior length thereof, the resistance wire being insulated withrespect to the guide tube by insulating material 62b and is electricallyconnected to a conventional electrically operated fuel level indicator64, the fuel level indicator also being connected in an electricalcircuit with a suitable source of electrical power, such as the vehiclebattery 65, through an ignition switch SW-l and to the solenoid valveSOL-V and to the fuel pump FP-3.

Slidably encircling the float guide tube is a ring-type float 66carrying thereon electrical wiper contacts 67 connected together by aconductor not shown. One contact 67 contacts the resistance wire 63 andthe other contacts the float guide tube 62. The amount of resistance inthis circuit is directly proportional to the level of liquid in thisreservoir.

This portion of the electrical circuit of the dual fuel system is suchthat, assuming ignition switch SW-l is closed, when the level of thehigh volatility fuel distillate in the reservoir portion 61 of thedistillation unit 40 is below a set level position, as sensed by thewiper contact 67 on the float 66 engaging the calibrated resistance wire63, the electrical circuit is completed through the fuel level indicator64, in a known manner, to energize the solenoid valve SOL-V so that withthe fuel pump FP-l in operation, fuel is continuously supplied to thedistillation unit and, at the same time, the fuel pump FP-3 is energizedto pump the fuel discharged through conduit 26 from the distillationunit back to the fuel reservoir 20. As the float 66 with the wipercontact 67 thereon reaches a predetermined position to indicate that thereservoir unit is full of liquid high volatility fuel, the solenoidvalve SOL-V is deenergized, as is the fuel pump FP-3. Since the solenoidvalve SOL-V is a normally closed valve, the deenergization of this valvewill block the flow of raw fuel to the distillation unit 40 until suchtime as the liquid level of the high volatility fuel within this unitagain drops below the full fuel distillate level. Fuel pump F P-3 isused to ensure positive return of the undistilled fuel to the fuelreservoir 20.

Referring now to FIG. 3, the float bowl 12a of the carburetor issupplied with regular fuel either directly 4 from the fuel tank 20through conduit 22 or with high volatility fuel from the distillationunit 40 through conduit 34 as controlled by the shutle valve 23. Theshuttle valve 23 may be of any suitable type and, in the embodimentillustrated, includes a housing 70 having an elongated chamber 71therein, the opposite end walls of the housing being curved to providevalve seats 72 for a ball 73 loosely movable in the chamber 71 toselectively control the flow through either the inlet passage 74 in thevalve housing connected to the conduit 22 or through the inlet passage75 connected to conduit 34, with discharge from the chamber 71 beingthrough a centrally located discharge port 76 connected by the conduit24 to the float 12a of the carburetor, fuel flow into the float bowlbeing controlled by a conventional float valve 77 therein. Whenever fuelunder pressure is introduced at one of the inlet passages 74 or 75, theball 73 will move to the other end of chamber 71 to seal off the otherinlet passage and to permit flow of fuel through discharge port 76.

In addition, a float bowl drain system is provided for the carburetor 12and in the embodiment disclosed includes a drain passage 78 extendingfrom the bottom of the float bowl into a piston-type valve 80 controlledpiston chamber 81 in the body of the carburetor with liquid flowtherefrom through a passage 82 connected to the conduit 36 to permit thereturn of fuel drained from the float bowl 12a to the fuel tank 20. Flowthrough the drain passage 78 is controlled by valve 80 slidably mountedin the chamber 81 and which is normally biased out of engagement withthe valve seat surrounding the drain passage 78 by a coiled spring 83.The valve 80 is closed to block flow from the drain passage 78 by fuelpressure supplied to the piston portion of the valve 80 through aconduit 84 operatively connected at one end to the piston chamber andits other end to the conduit 24 whereby, as fuel is being supplied tothe float bowl via the fuel pumps FP-l or FP-Z through the shuttle valve23 and conduit 24, this fuel under pressure will pass through theconduit 84 and force the valve 80 into position to block flow of fuelfrom drain passage 78 whereby, as long as fuel is being supplied underpressure to the float bowl 12a of the carburetor, draining of fuel fromthe float bowl will be prevented.

A clearer understanding of the operation of the dual fuel system forsupplying fuel to the engine and of the electrical circuit controllingthe various elements of this system can best be obtained by reference tothe schematic wiring diagram of FIG. 4. When the ignition switch SW-l isclosed, electrical power from the battery 65 is directed to a snapaction temperature switch SW-2 which is suitably immersed, not shown, inthe engine coolant fluid in engine It If the coolant temperature isbelow a predetermined temperature, for example 140 F., the temperatureswitch SW-2 directs electrical power to the fuel pump FP-Z so that thispump is operative to pump high volatility fuel from the reservoir of thedistillation unit 40 through the shuttle valve 23 and into the floatbowl 12a of carburetor 12 for use in engine 10. When the coolanttemperature reaches the above-identified predetermined temperature, thetemperature switch SW-2 then snaps to its alternate position directingelectrical power to the fuel pump FP-l while, of course, at the sametime de-energizing fuel pump FP-2 and this pump stops pumping.Accordingly, the fuel pump FP-l then pumps regular fuel from the fuelreservoir to the float bowl of the carburetor through shuttle valve 23so that the switch is then made from the use of high volatility fuel tothe use of normal fuel in engine 10 for continued operation of theengine, the fuel pump FP-l also being used to pump raw fuel to thedistillation unit 40 in the manner previously described.

Also, as previously described, during engine operation with the ignitionswitch SW-l closed, the fuel pump F P-3 is operated when thedistillation unit 40 is in operation to pump undistilled fuel from thisunit back to the fuel reservoir 20.

When the ignition switch SW-l is opened, both fuel pumps FP-l and FP-2,used in the manner described above to supply fuel to the carburetor,cease pumping and the fuel pressure closing the float bowl drain valve80 will reduce to nearly zero pounds per square inch gauge pressure thuspermitting the spring 83 to effect unseating of the valve 80 to permitdraining of fuel from the float bowl 12a through the drain passage 78into conduit 36 for return to the fuel reservoir 20. With the float bowl12a empty of fuel, when the ignition switch SW-l is again closed, eitherfuel pump FP-l or FP-2 will be energized, depending on coolanttemperature as sensed by the temperature switch SW-2, to pump fuelthrough the shuttle valve 23 to fill the float bowl 120 with fuel.

What is claimed is:

l. A dual fuel system for an internal combustion engine having a coolingsystem containing coolant fluid heated during engine operation and afuel induction system including a carburetor having a float bowl, saiddual fuel system including a fuel reservoir for regular fuel, valvemeans having a first inlet, a second inlet and a discharge port, aconduit connecting said discharge port of said valve means to the floatbowl of the carburetor, a distillation unit including a condenser tubehousing having cooling fins on the exterior thereof, a fuel evaporationunit, having an outer, helical fuel flow path, positioned in the upperend of said condenser tube housing and spaced from the bottom thereof toi provide a reservoir for a distillate therein, an undistilled fuelcollecting means positioned in said condenser tube housing beneath saidfuel evaporation unit for collecting undistilled fuel flowing from saidfuel evoparation unit, first conduit means including a first pump meansconnecting said fuel reservoir to said first inlet of said valve meansand to said fuel evaporation unit to supply fuel to said helical fuelflow path, second conduit means including a second pump means connectedto said condenser tube housing in fluid flow communication with saiddistillate reservoir and to said second inlet of said valve means, thirdconduit means connecting said undistilled fluid collecting means to saidfuel reservoir, passage means in said fuel evaporation unit for thecirculation-of coolant fluid therein in heat exchange relationship tosaid helical fuel flow path, conduit means connecting the cooling systemof the engine to said passage means for recirculation of coolant fluidthrough said passage means, and temperature sensing control meansoperatively connected to said first pump means and said second pumpmeans positioned in ther' mal relationship to the coolant fluid in thecooling system to selectively effect operation of said first pump meansand said second pump means as a function of coolant temperature.

2. A dual fuel system according to claim 1 further including float bowldrain means having a drain conduit means connected at one end to thefloat bowl of the carburetor for draining fuel therefrom and connectedat its opposite end to said third conduit means, and bydrauliccontrolled valve means positioned in said drain conduit means andoperatively connected in fluid communication with said conduit andoperative to prevent flow through said drain conduit means when fuelunder pressure is being pumped through said conduitv 3. A dual fuelsystem according to claim 1 further including a distillate level sensingmeans operatively positioned in said distillate reservoir of saidcondenser tube housing and, valve means positioned in said first conduitmeans and operatively connected to said distillate level sensing meansto control the flow of fuel to said fuel evaporation means as a functionof the level of distillate in said reservoir as sensed by saiddistillate level sensing means.

1. A dual fuel system for an internal combustion engine having a coolingsystem containing coolant fluid heated during engine operation and afuel induction system including a carburetor having a float bowl, saiddual fuel system including a fuel reservoir for regular fuel, valvemeans having a first inlet, a second inlet and a discharge port, aconduit connecting said discharge port of said valve means to the floatbowl of the carburetor, a distillation unit including a condenser tubehousing having cooling fins on the exterior thereof, a fuel evaporationunit, having an outer, helical fuel flow path, positioned in the upperend of said condenser tube housing and spaced from the bottom thereof toprovide a reservoir for a distillate therein, an undistilled fuelcollecting means positioned in said condenser tube housing beneath saidfuel evaporation unit for collecting undistilled fuel flowing from saidfuel evoparation unit, first conduit means including a first pump meansconnecting said fuel reservoir to said first inlet of said valve meansand to said fuel evaporation unit to supply fuel to said helical fuelflow path, second conduit means including a second pump means connectedto said condenser tube housing in fluid flow communication with saiddistillate reservoir and to said second inlet of said valve means, thirdconduit means connecting said undistilled fluid collecting means to saidfuel reservoir, passage means in said fuel evaporation unit for thecirculation of coolant fluid therein in heat exchange relationship tosaid helical fuel flow path, conduit means connecting the cooling systemof the engine to said passage means for recirculation of coolant fluidthrough said passage means, and temperature sensing control meansoperatively connected to said first pump means and said second pumpmeans positioned in thermal relationship to the coolant fluid in thecooling system to selectively effect operation of said first pump meansand said second pump means as a function of coolant temperature.
 2. Adual fuel system accordinG to claim 1 further including float bowl drainmeans having a drain conduit means connected at one end to the floatbowl of the carburetor for draining fuel therefrom and connected at itsopposite end to said third conduit means, and hydraulic controlled valvemeans positioned in said drain conduit means and operatively connectedin fluid communication with said conduit and operative to prevent flowthrough said drain conduit means when fuel under pressure is beingpumped through said conduit.
 3. A dual fuel system according to claim 1further including a distillate level sensing means operativelypositioned in said distillate reservoir of said condenser tube housingand, valve means positioned in said first conduit means and operativelyconnected to said distillate level sensing means to control the flow offuel to said fuel evaporation means as a function of the level ofdistillate in said reservoir as sensed by said distillate level sensingmeans.